Agree, to offer specific recommendation to the question(s) here we need to see the server script, since that it where the desired part and welds would be created.
If the server script is not placing and welding the placed part, have you confirmed that the server script is at least receiving the FireServer event and data payload… and then successfully calling an appropriate function to execute on that event?
For the purpose of experimenting and testing (or even other intents), you can create a single LocalScript that creates does ALL of your work to produce a placed part and weld locally. This only affects the client workspace, but would necessarily include all the functions needed. When that works, you can copy the required functions into a server script and add in the RemoteEvent handling.
Meanwhile, you may be interested in this tutorial from @EgoMoose, although it restricts placement to “Canvas objects” and so does not address the “place anywhere on any surface” need directly. However, it does a good job of explaining and organizing the concepts involved, and how to go about structuring the scripts involved. Also, as discussed in another thread, this tutorial internally operates on a 2D XY plane (regardless of how that plane is oriented in 3D world space!), and is only a tutorial.